1. Field of the Invention
The present invention relates to a pair of binoculars, and more particularly to a pair of binoculars making it possible to easily perform a focusing operation and a diopter adjustment, and efficiently perform an assembling operation.
2. Prior Art
Up to now, there has been demanded a structure making it possible to easily perform a focusing operation and a diopter adjustment in an optical device such as a pair of binoculars and the like.
As a pair of binoculars making it possible to easily perform a focusing operation and a diopter adjustment, there has been proposed, for example, “a pair of binoculars in which two pipe members (1, 1′) of said pair of binoculars are connected with each other through two bridges (2, 3) each having a joint in order to adjust an interpupillary distance, said two bridges turn around the axes of joints (4) and are disposed distantly from each other by a specified distance with no connection by the central axis in order to form a penetrating portion (6), said two pipe members (1, 1′) have a focusing gear (8) being axially movable for focusing, said focusing gear is operated by a common rotary knob (12) and a gear, said gear extends through one of said bridges (2 or 3) having joints from said rotary knob (12) to said focusing gear (8), and an interpupillary adjustment has no influence on focusing” (see patent literature 1).
[Patent literature 1] Japanese Patent Laid-Open Publication No. 2000-56237 (claim 1)
Hereupon, in the invention described in said patent literature 1, there is performed a focusing operation as described as “A rotary knob is turned at a position where it has been inserted for focusing a pair of binoculars. The turning of the rotary knob is transferred from a rotary knob shaft directly to a friction disk and a projection. The projection engages the friction disk with a helical gear. The turning of the rotary knob is converted into an axial movement of a stop member by the helical gear, and an angular lever moves a focusing gear in the axial direction by an end portion having a fork. Since when a pipe member is turned around the axis the angular lever slides on a conical stop member at its end portion without the action of a gear for converting the turning of the knob into an axial movement of the focusing gear, in a pair of binoculars of the present invention a focusing operation is performed independently of an interpupillary adjustment.” (See paragraphs [0030] and [0031] in patent literature 1.)
And in the invention described in patent literature 1 described above, a rotary knob is turned around a joint axis by moving radially an angular lever in order to perform a diopter adjustment. As a result, the turned rotary knob moves a fixed focusing gear in the axial direction.
As described above, in the invention described in patent literature 1, since the amount of movement of a focusing gear in the axial direction is adjusted in order to perform a diopter adjustment, it is necessary to perform such adjustment at plural points as positional adjustment between an angular lever and a supporter, positional adjustment between a coupler and a joint axis, and the like. In the invention described in patent literature 1, therefore, there is a problem that since the above-mentioned members also need to be adjusted in position when assembling the whole of a pair of binoculars it is not possible to efficiently perform the operation of assembling.